Fax machine and method of performing handshaking process based on T.30 protocol

Abstract

A method of performing handshaking between fax machines on the basis of T.30 protocol includes transmitting information on a first data rate selected to transmit a fax document to a receiving-side fax machine, transmitting a plurality of frames including bit strings predefined to test data transmission/reception at the first data rate prior to transmitting the fax document to the receiving-side fax machine, and receiving a message informing success or failure of the test. The transmitting of the frames includes determining a time duration of the transmitting the frames based on at least one of a TCF flag value and the first data rate.

What is claimed is: 
     
       1. A method of performing handshaking between fax machines on the basis of T.30 protocol, wherein a sending-side fax machine:
 transmits information on a first data rate selected to transmit a fax document, to a receiving-side fax machine; 
 transmits a plurality of frames including one or more bit strings to the receiving-side fax machine, which are predefined to test data transmission/reception at the first data rate prior to transmitting the fax document; and 
 receives a message informing success or failure of the test, and 
 wherein the transmitting of the frames comprises determining a time duration of the transmitting the frames based on at least one of a TCF flag value set to the sending-side fax machine and the first data rate. 
 
     
     
       2. The method of  claim 1 , wherein the transmitting of the frames further comprises:
 checking whether the TCF flag value is set; and 
 increasing the time duration of the transmitting the frames when the TCF flag value is set. 
 
     
     
       3. The method of  claim 2 , wherein:
 the transmitting of the frames comprises transmitting the frames for a first time duration when the TCF flag value is not set and transmitting the frames for a second time duration when the TCF flag value is set; and 
 the first time duration is 1.5 seconds±an error of 10% and the second time duration exceeds the first time duration. 
 
     
     
       4. The method of  claim 1 , further comprising:
 providing a graphic user interface to select a custom mode to change the time duration; and 
 activating the TCF flag value when the custom mode is selected. 
 
     
     
       5. The method of  claim 1 , wherein the transmitting of the frames comprises:
 checking a previous transmission history of one or more fax documents to the receiving-side fax machine; and 
 activating the TCF flag value when there is a transmission failure history, as a result of the checking. 
 
     
     
       6. The method of  claim 1 , wherein the transmitting of the frames comprises:
 comparing the first data rate with a threshold preset to the sending-side fax machine; and 
 increasing the time duration when the first data rate is lower than or equal to the threshold. 
 
     
     
       7. The method of  claim 1 , further comprising:
 determining whether the first data rate is the lowest data rate of the sending-side fax machine when the message informing the failure of the test is received; 
 increasing the time duration required to transmit the frames when it is determined that the first data rate is the lowest data rate of the sending-side fax machine; and 
 retransmitting the frames on the basis of the increased time duration. 
 
     
     
       8. The method of  claim 7 , wherein, when the message informing the failure of the test is received again after the retransmitting of the frames, the retransmitting of the frames is repeated with increasing the time duration step by step until the message informing the success of the test is received. 
     
     
       9. The method of  claim 7 , wherein when it is determined that the first data rate is not the lowest data rate of the sending-side fax machine, the retransmitting of the frames are repeated with decreasing a data rate step by step until a message informing the success of the test is received. 
     
     
       10. The method of  claim 1 , further comprising:
 initializing the TCF flag value if the message informing the success of the test is received. 
 
     
     
       11. A non-transitory computer-readable storage medium to contain computer-readable codes as one or more programs to execute the method of  claim 1 . 
     
     
       12. A sending-side fax machine to perform handshaking with a receiving-side fax machine on the basis of T.30 protocol, the fax machine comprising:
 a scanning module to scan a fax document to be transmitted; 
 a storage unit to store the scanned fax document; 
 a network interface to transmit the fax document through a public switched telephone network (PSTN) or a voice over internet protocol (VoiP) network; and 
 a control unit to control the network interface to transmit information on a first data rate selected to transmit the fax document to the receiving-side fax machine, to transmit a plurality of frames including one or more bit strings predefined to test data transmission/reception at the first data rate prior to transmitting the fax document to the receiving-side fax machine, and to 
 receive a message informing success or failure of the test, 
 wherein the control unit determines a time duration of the transmitting the frames based on at least one of a TCF flag value set to the sending-side fax machine and the first data rate. 
 
     
     
       13. The fax machine of  claim 12 , wherein the control unit checks whether the TCF flag value is set, and increases the time duration of the transmitting the frames when the TCF flag value is set. 
     
     
       14. The fax machine of  claim 13 , wherein:
 the control unit transmits the frames for a first time duration if the TCF flag value is not set and transmits the frames for a second time duration if the TCF flag value is set; and 
 the first time duration is 1.5 seconds±an error of 10% and the second time duration exceeds the first time duration. 
 
     
     
       15. The fax machine of  claim 12 , wherein:
 the control unit provides a graphic user interface to select a custom mode to change the time duration; and 
 the control unit activates the TCF flag value when the custom mode is selected. 
 
     
     
       16. The fax machine of  claim 12 , wherein the control unit checks a previous transmission history of one or more fax documents to the receiving-side fax machine and activates the TCF flag value if there is a transmission failure history, as a result of the checking. 
     
     
       17. The fax machine of  claim 12 , wherein the control unit compares the first data rate with threshold preset to the sending-side fax machine and increases the time duration required to transmit the frames when the first data rate is lower than or equal to the threshold. 
     
     
       18. The fax machine of  claim 12 , wherein the control unit determines whether the first data rate is the lowest data rate of the sending-side fax machine when the message informing the failure of the test is received, increases the time duration required to transmit the frames when it is determined that the first data rate is the lowest data rate of the sending-side fax machine, and retransmits the frames for the increased time duration. 
     
     
       19. The fax machine of  claim 18 , wherein when the message informing the failure of the test is received again after retransmitting the frames, the control unit repeats an operation of retransmitting the frames with increasing the time duration step by step until the message informing the success of the test is received. 
     
     
       20. The fax machine of  claim 18 , wherein when it is determined that the first data rate is not the lowest data rate of the sending-side fax machine, the control unit repeats an operation of retransmitting the frames with decreasing a data rate step by step until the message informing the success of the test is received.